Search for an electroweak tensor contribution using trapped ⁸Li with the Beta-decay Paul Trap Mk IV

The Beta-decay Paul Trap (BPT) measures the beta-neutrino angular correlation coefficient a_βν in the Gamow-Teller decays of ⁸Li and ⁸B (decaying to ⁸Be^∗→2α) to search for a tensor component of the weak interaction, a beyond-Standard Model possibility. The new BPT Mk IV trap reduces β-scattering by a factor of 4, a key source of systematic uncetainty, and has recently been commissioned with ⁸Li with 2.7 million triple coincidence events. In addition, a complete detector characterization has been performed with an α beam to reduce systematic uncertainties associated with the silicon strip detector response. This new high-statistics ⁸Li data set, coupled with the experimental advancements, will allow for improved sensitivity to a tensor contribution. In the near future, the BPT should be able to reach an uncertainty of ?|C_T /C_A|² ≤ 10⁻³, though the theoretical understanding of the nuclear structure still requires improvement.